Each page details 30 customers' names, their account and sort code numbers and how much they have paid in and out.

Stunned Stephanie said yesterday: "I did not expect them to be so lax with security as to be sending out private and confidential information of so many of their customers.

"In the wrong hands these documents would allow criminals to run amok through people's personal and financial lives." The mum-of-one, from Aberdeen, wrote to her local branch in a bid to reclaim bank fees.

She said: "I wanted to add up all the bank charges they have taken from me over the years. All I wanted was a list of my own charges so I can seek a refund of the some of the costs they have deducted from me.

"Imagine my surprise when I found five packages containing 500 sheets of customers' names, account details and sort codes had been sent to me.

"They're quick to hit us in the pocket. I wonder if they'll make a refund to each customer affected by this?" The packages are now being returned to HBOS.

The bank, alerted to the scandal by the Daily Mirror, has apologised and is launching an immediate inquiry.

Stefanie's partner Kevin added: "It's embarrassing when any bank makes a mistake and apologises to one customer, so you understand the size of the mistake when they're apologising to 75,000."

A spokeswoman at the bank's Edinburgh HQ said: "We thank the Daily Mirror for bringing this to our attention. We'll investigate this as a matter of urgency.

"We'd like to apologise to all our customers involved for the inconvenience this may have caused."